81623779 has 2 divisors, whose sum is σ = 81623780. Its totient is φ = 81623778.

The previous prime is 81623767. The next prime is 81623797. The reversal of 81623779 is 97732618.

It is a happy number.

Together with next prime (81623797) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81623779 - 2⁵ = 81623747 is a prime.

It is not a weakly prime, because it can be changed into another prime (81653779) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40811889 + 40811890.

It is an arithmetic number, because the mean of its divisors is an integer number (40811890).

Almost surely, 2^81623779 is an apocalyptic number.

81623779 is a deficient number, since it is larger than the sum of its proper divisors (1).

81623779 is an equidigital number, since it uses as much as digits as its factorization.

81623779 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 127008, while the sum is 43.

The square root of 81623779 is about 9034.5879264082. The cubic root of 81623779 is about 433.7827049728.

The spelling of 81623779 in words is "eighty-one million, six hundred twenty-three thousand, seven hundred seventy-nine".